This invention relates to string trimmers. In recent years, string trimmers have enjoyed a well-deserved popularity. These trimmers use a string or flexible line as a cutting medium, usually a monofilament nylon line, which is rotated at high speed. String trimmers are efficient devices for trimming grass, weeds, etc.
Due to the stresses placed on the trimming line, the trimming line will break from time to time during use of the trimmer. To facilitate the replacement of broken segments of the trimming line, the commercial string trimmers usually carry a supply of the line and some arrangement for feeding the replacement line into operating position relative to the head of the trimmer. The commercially-used feeding arrangements can generally be broken down into two classes: (1) manual feed devices, and (2) automatic feed devices. The manual feed devices are usually less complicated and less costly than the automatic feed devices. Unfortunately, prior to the present time, the manual feed devices have been much less convenient than the automatic feed devices. In fact, it is apparent that the market for automatic feed devices has been created principally due to the inconvenience inherent in feeding line using the commercially-available manual feed devices.
This invention lies, in part, in the discovery that the inconvenience inherent in manual feed devices can be attributed in substantial part to the spool for storing the trimming line. Particularly, manual feed devices often require several operations involving the storage spool. Firstly, the spool must be released for rotation, then rotated, and finally secured from additional rotation. At the same time, the line must be guided or fed outwardly from the spool through an appropriate slot or opening. These steps often involve several manual manipulations of the feed device. Remembering that these devices are used only occasionally, the user may not develop the manipulative skills to enable him to efficiently accomplish these manual feed operations. In any event, the user is likely to find these manual feed operations to be inconvenient at least to some degree.
This invention provides a manual feed device which does not use a storage spool and thereby eliminates many of the manual feed difficulties. According to the present invention, the line is disposed in a coil within a spoolless housing in a fashion where it may be center fed from the coil without rotation of the bulk of the line. Since the spool is eliminated, there is no need to release the spool for feeding rotation, or to rotate the spool to feed line therefrom, or to secure the spool against rotation during operation of the trimmer. Since these manipulative steps are not required with the feed device of the present invention, the trimming line may be fed from the device with relative ease.
Also, importantly, this invention provides several novel structures for conveniently clamping or otherwise securing the line during operation of the trimmer and for releasing the line for feeding line from the storage coil.
The spoolless feature, in combination with the convenient line securing and releasing arrangements, provide a manual feed device for string trimmers which features a level of convenience nearing that of the automatic feed line trimmers. Moreover, the present invention provides a trimming head which is simple in construction and is relatively inexpensive to manufacture.
A first embodiment of a manual feed line trimmer according to this invention features a head comprising a housing formed of a cover and a base, for containing the coiled supply of trimming line. The cover is attached to the drive shaft of the motor for the trimmer so that the head may be rotated at high speed. The base has a central opening through which the line is fed and also preferably has a radial, partially-enclosed passage extending from the central opening to the periphery of the head through which the trimming line is fed to project radially-outwardly from the head so that it may accomplish its trimming task when the lead is rotated at high speed. The radial passage preferably has a rounded contour in the plane of rotation near the radially-outward portion of the passage to minimize line stress and breakage. The head also features a clamp comprising an axially movable clamping member associated with the housing which projects downwardly toward the central opening in the base and which is adapted to engage and clamp the line at the center opening in the base. The clamping member is preferably resiliently biased downwardly into the central opening of the base by an axial spring. The clamping member can be raised from the central opening in the base to release the line for feeding line from the head by movement of a lever which in turn rotates a cam integral with the lever which lifts the clamping member as it rotates.
A second exemplary embodiment of a string trimming head according to this invention also comprises a similar housing for storing the coiled trimming line. However, the second embodiment features a pair of jaw members or clamping members having opposed clamping surfaces for clamping the trimming line. The jaw members are disposed on opposite sides of a radial slot or passageway in the base through which the trimming line is fed to project the trimming line outwardly from the head. The jaw members are slidable generally in respective directions along a guideway for the jaw members so that radially-inward movement of the jaw members causes the opposed clamping surfaces of the jaw members to separate to release the trimming line, and so that radially-outward movement of the jaw members causes the opposed clamping surfaces of the jaw members to converge to clamp the trimming line. A button member can be provided which may be depressed for moving the jaw members radially-inwardly. The jaw members are biased radially-outwardly by a spring so that, upon release of the button member, the jaw members will slide radially-outwardly along the guideway under the influence of the spring to move close the jaw members into clamping engagement with the trimming line.
A third exemplary embodiment is similar to the second embodiment except that the jaw members are attached to the base for pivotal movement away from each other to release the trimming line when the button member is depressed and for pivotal movement toward each other under the influence of a spring to provide clamping engagement of the trimming line when the button member is released.
A fourth exemplary embodiment is similar to the first exemplary embodiment in that it features a clamp which is disposed adjacent to the central opening in the base. However, in the fourth embodiment, one clamping face of the clamp is on the cover and the other opposed face of the clamp is on the base. The cover and base are threadably engaged so that clamping faces are axially movable toward and away from each other by rotation of the cover relative to the base. Consequently, such relative rotation of the cover and base moves the clamping faces either together to secure the trimming line during operation of the trimmer or apart to release the trimming line for feeding replacement line from the storage coil, depending on the direction of relative rotation of the cover and base.
A fifth exemplary embodiment also uses a housing formed by a cover and a base for containing the storage coil. However, in the fifth embodiment, the clamping means is integrally formed with the base. The clamping means consists of a fixed jaw and a movable jaw, the latter being formed on a radially-inwardly-projecting lever which is cantileverly attached to the base near the periphery thereof. The fixed and movable jaws cooperate to secure the trimming line. The movable jaw lever may be axially-inwardly depressed to cause the jaws to separate to release the trimming line. Upon release of the movable jaw lever, the jaw members move toward each other by virtue of the resiliency of the material from which the base is formed so as to clamp the trimming line.
Note that each of the embodiments features a spoolless trimming head. Consequently, there is no spool which must be released for rotation, rotated to feed trimming line and then secured from rotation prior to operation of the trimmer. Each of the embodiments of this invention enables the user to merely pull the line from the trimmer when the clamp is released by depressing a clamping member or otherwise operating the clamp. In each case (except the fourth embodiment of this invention), release of the clamping member automatically reapplies the clamp so that the trimming head is again ready for operation.
Although the present invention is principally described in connection with a manual-feed string trimmer head, some of the principles and features of the present invention may be incorporated in an automatic-feed string trimmer head. Other features and advantages of the present invention will become apparent in view of the detailed description of the preferred embodiments appearing hereinafter.